The results of research on the water relations and irrigation needs of sugar
cane are collated and summarized in an attempt to link fundamental studies on
crop physiology to irrigation practices. Background information on the centres
of production of sugar cane is followed by reviews of (1) crop development,
including roots; (2) plant water relations; (3) crop water requirements; (4)
water productivity; (5) irrigation systems and (6) irrigation scheduling. The
majority of the recent research published in the international literature has
been conducted in Australia and southern Africa. Leaf/stem extension is a more
sensitive indicator of the onset of water stress than stomatal conductance or
photosynthesis. Possible mechanisms by which cultivars differ in their responses
to drought have been described. Roots extend in depth at rates of 5-18 mm d-
1 reaching maximum depths of > 4 m in ca. 300 d providing there are no physical
restrictions. The Penman-Monteith equation and the USWB Class A pan both give
good estimates of reference crop evapotranspiration (ETo). The corresponding
values for the crop coefficient (Kc) are 0.4 (initial stage), 1.25 (peak season)
and 0.75 (drying off phase). On an annual basis, the total water-use (ETc) is in
the range 1100-1800 mm, with peak daily rates of 6-15 mm d-1. There is a linear
relationship between cane/sucrose yields and actual evapotranspiration (ETc)
over the season, with slopes of about 100 (cane) and 13 (sugar) kg (ha mm)-1
(but variable). Water stress during tillering need not result in a loss in yield
because of compensatory growth on re-watering. Water can be withheld prior to
harvest for periods of time up to the equivalent of twice the depth of available
water in the root zone. As alternatives to traditional furrow irrigation, drag-
line sprinklers and centre pivots have several advantages, such as allowing the
application of small quantities of water at frequent intervals. Drip irrigation
should only be contemplated when there are well-organized management systems in
place. Methods for scheduling irrigation are summarized and the reasons for
their limited uptake considered. In conclusion, the ‘drivers for change',
including the need for improved environmental protection, influencing technology
choice if irrigated sugar cane production is to be sustainable are summarize